The present invention relates generally to systems and methods for determining impact locations of projectiles on targets. More specifically, the present invention relates to a system for determining the impact location of a projectile on a damage resistant target.
The location of impact of a projectile is of interest in a number of different fields including weaponry and sports. For example, when a user is trained in firing a weapon, it is common to practice at a static firing range in which the user fires a weapon at targets which are remote from the firing point. Various systems and methods have been developed for determining locations of impact of such projectiles and providing the impact location information to the user.
Some prior art systems employ acoustic sensors for sensing an airborne acoustic signal generated by a projectile and for determining the location at which the projectile passes through or strikes a predetermined plane. For example, one such system includes microphones arrayed around a destructible target medium, such as heavy paper, rubber, or plastic sheeting. The sound of a projectile punching through the medium is detected by the microphones. The time difference of arrival of the sound is calculated between the microphones, and a location for the xe2x80x9cpunch throughxe2x80x9d point is then determined.
Unfortunately, since the target is damaged each time a projectile strikes the target medium, it is necessary to constantly roll, advance, or otherwise replace that portion of the target which has been destroyed by the previously fired projectile. In addition, such acoustically based destructible medium impact location systems are not designed to be xe2x80x9cmissedxe2x80x9d. In other words, the target medium transport and alignment hardware and the microphones are not designed to endure the shock from repeated strikes. These problems contribute undesirably to the expense of operating and maintaining such a destructible target medium impact location system.
In acoustically based impact location systems, mathematical formulas for locating impact locations through time difference of arrival of an airborne sound wave depend upon the application of a velocity of sound value which is constant for the airborne sound wave. The velocity of sound through air is unstable, and highly dependent upon atmospheric conditions. Thus, the application of a constant velocity of sound value to the mathematical formulas introduces calculation errors. In addition, since the mathematical formulas depend upon the application of a constant velocity of sound value, the distance between microphones is a major factor in determining accuracy. Accordingly, an increase in target size, and hence, distance between the microphones located at the perimeter of the target, results in decreasing of accuracy.
Other prior art impact location systems employ a destruction resistant target medium, such as steel, that mitigate the problems associated with the destructible target medium impact location systems. One such system employs piezoelectric type sensors arrayed about the perimeter of the destruction resistant target. The target area around a sensor defines a sector for that sensor. As a projectile strikes the target, the impact is registered by the sensors. The approximate impact location is determined by using the sensor signals and logic circuitry. A lamp is then lit to indicate in which of the sensor sectors the impact is located.
Unfortunately, this system does not provide the precise point at which the projectile strikes the target. Furthermore, since the sensors are spaced around the periphery of the target, the sensors may be hit by the projectiles. Thus, this system also suffers from the disadvantage of additional expenses resulting from the need to replace damaged sensors at frequent intervals.
Accordingly, it is an object of the present invention to provide a system for determining an impact location of a projectile.
Another object of the present invention is to provide an impact location determination system which employs a damage resistant target medium.
Another object of the present invention is to provide precise impact location information to a user.
Another object of the present invention is to provide an impact location system that accommodates large target areas without sacrificing accuracy.
Yet another object of the present invention is to provide an impact location system that has a processing speed that accommodates rapid fire projectiles.
The above and other advantages of the present invention are carried out in one form by a system for determining an impact location of a projectile. The system includes a plate having a planar surface adapted to be impacted by the projectile. A plurality of pressure sensors are disposed in the plate for detecting a pressure disturbance event outwardly propagating through the plate from the impact location on the planar surface. A signal processing circuit is in electrical communication with the pressure sensors for measuring time difference of arrivals of the pressure disturbance event between the pressure sensors and for determining the impact location in response to the time difference of arrivals.
The above and other advantages of the present invention are carried out in another form by a method for determining an impact location of a projectile on a strike plate in response to a pressure disturbance property particular to the strike plate, the pressure disturbance property being a pressure disturbance propagation velocity. The method calls for detecting, at each of a plurality of pressure sensors coupled to the strike plate, a pressure disturbance event exhibiting the propagation velocity, the pressure disturbance event outwardly propagating from the impact location of the projectile on the strike plate. The method further calls for measuring time difference of arrivals of the pressure disturbance event between the pressure sensors and determining the impact location in response to the time difference of arrivals and the pressure disturbance propagation velocity, the pressure disturbance propagation velocity being less than the velocity of sound in the strike plate.